Can the performance of graphenenanosheets for lithium storage in Li-ion batteries be predicted?

Abstract

Graphene nanosheets (GNS) were prepared from graphitic oxide (GO) in two different ways: (a) thermal exfoliation at different temperatures; and (b) wet chemistry, using aqueous N₂H₄ and KBH₄ as reducing agents. Irrespective of the synthetic method used, the materials exhibited a high irreversible capacity and strong polarization in their charge curves, when used in a Li-ion battery. The GNS synthesized with N₂H₄ exhibited the best performance. Thus, at 149 mA g⁻¹ the average specific capacity delivered was ca. 600 mA h g⁻¹ after 100 cycles. On the other hand, the worst performance, irrespective of rate, was that of GNS synthesized with KBH₄ and the thermal GNS obtained at 800 °C. The physical and chemical analyses allowed various parameters to be derived for correlation with the electrochemical properties. Unfortunately, no clear-cut correlation was apparent. A comparison with reported data revealed that no correlation appears to exist with physical and chemical properties that allows a simple strategy for tailoring an effective graphene anode to be designed.